The human spine is a biomechanical structure consisting of thirty-three vertebral members and is responsible for protecting the spinal cord, nerve roots and internal organs of the thorax and abdomen. The spine also provides structural support for the body while permitting flexibility of motion.
Surgery on the spine may sometimes be necessary because of, for example, physical trauma or degenerative diseases. After spinal surgery, it is frequently necessary to apply a vertebral plate to lock adjacent vertebrae together to induce fusion of those vertebras. Medical bone screws are placed through the holes in the plates, and into the body of the vertebra. Often it is found that these screws do not find suitable core material in the bone to assure adequate long term mechanical strength, and the screws work loose and back out. The absence of a single screw over time in the assembly may not be detrimental to the success of fusion, but the screw becomes foreign matter in adjacent tissue and can cause severe complications to the patient.
There are numerous known plating systems that address this potential screw back-out problem, but they all require additional safety or backup hardware to retain the loose screws. Many require an internal set screw in the bone screw itself. This concept does what it is expected to do, but at the expense of the strength of the bone screw itself, as the screw has to be hollow. Other solutions require plates, tabs, or washers to retain the loose bone screw. In nearly every known solution, there is the potential of the solution becoming a problem. The more hardware installed, the more likely it is that there will be foreign matter getting into undesired places. There are the additional problems of complexity with all of these solutions. More things to tighten or secure means more work for the surgeon, and more levels of uncertainty.
Based on the foregoing, there is a need for an improved system and method for securing a vertebral plate to vertebrae with retaining screws.